Chester Wisniewski, a senior security adviser at Sophos, said he considers this a major problem. "In the digital age many organizations are collecting massive amounts of information on their users/customers and stashing it away in case it may be useful in the future," he said. "This has resulted in many data breaches disclosing far more than necessary, simply because organizations are hoarding information."

Wisniewski said getting rid of confidential data ought to be a routine, "trivial action." But, it becomes more difficult "if it wasn't factored into the original design of the data structures."

Part of the problem is that it is so easy and inexpensive to hoard information. In digital form, it's not like you're going to run out of file cabinets. "People think of it as this gold mine of data that they may want to mine later," Wisniewski said. "And it's not like a storage locker.."

"We've never had this capability before -- it's so easy to store more and more," he said. "But people typically responsible for collecting it aren't necessarily aware of how easy it might be for anybody to get it."

Dean Gonsowski, senior eDiscovery counsel for Symantec, told Dark Reading that as the collected information grows, so do the risks -- risks of data breaches, compliance problems if the data isn't kept according to laws and regulations, and added litigation cost if a judge orders a company to search its data for specific information.

Beyond that, he said that too many organizations don't even know how to distinguish between data they need to keep and what should be discarded. Even companies with policies on data destruction may have it written in terms that are too general, and may not have the IT capability to manage the policy.

Dark Reading cites a recent poll by the consulting firm Protiviti, which found that while 81% of respondents have a retain/discard policy for records, only 50% have a plan in place to decide what data needs to be kept.

Wisniewski said every enterprise will have different priorities. "It depends on what you consider valuable. From my perspective, I say keep nothing. But if you're going to keep stuff -- information on customers and marketing that include some [Personally Identifiable Information] and if you can't sort between what is sensitive and what's not, at least protect all of it with encryption."

Kevin McAleavey, cofounder and chief architect of the KNOS Project, said it should take only moderate effort to program a database to purge data that is no longer needed, and it is well worth it.

"All it takes to ruin any company's reputation is one single breach," he said. "The cost of such an incident far exceeds the cost of properly husbanding sensitive data, but sadly too many operations only realize those cost justifications after it's too late."

McAleavey said that when he and his wife started their business, "We designed technical diagnostics in the product so that absolutely zero PII is gathered, only technical data." And even data that "should be archived and moved offline as quickly as is possible."

Wisniewski says every enterprise, in both the public and private sector, should set up a system of classifying data. "Companies used to think they were inside a wall. Now with mobile, there isn't an inside and outside," he says. "Data is being accessed all over the globe by your own people and by the bad guys. So we are seeing some of them classify the data better. Almost like the military. Class A is always encrypted, so if it ends up on data stick that gets lost or stolen, it's still protected."

Still, he says, "We keep seeing breaches, because things like this just aren't on their [company CEOs] radar." He recalls the Sony breach from three years ago, because the company forgot about a server with credit card data. Or, the much more recent breach of medical records at the Utah Department of Health because data was not being erased daily, as its own security protocols required.

He suggests that companies too small to have a skilled security team should "outsource to a company that knows how to do it. If you are not prepared to invest in taking these steps, you shouldn't collect the data to begin with."